1. Field of the Invention
The present invention relates to an elastic wave device in which a lamination layer film and a piezoelectric thin film are laminated on a support substrate.
2. Description of the Related Art
A lamination layer film is provided on a support substrate in an elastic wave device disclosed in WO 2012/086639A1. A piezoelectric thin film is laminated on the lamination layer film. The lamination layer film includes a high acoustic velocity film and a low acoustic velocity film. The low acoustic velocity film is formed of a film where an acoustic velocity of a bulk wave propagating therein is smaller than an acoustic velocity of a bulk wave propagating in the piezoelectric thin film. The high acoustic velocity film is formed of a film where an acoustic velocity of a bulk wave propagating therein is larger than an acoustic velocity of an elastic wave propagating in the piezoelectric thin film.
In the elastic wave device disclosed in WO 2012/086639A1, the piezoelectric thin film is made of a piezoelectric single crystal, such as LiTaO3 or the like. Because of this, the piezoelectric thin film is likely to be cracked or chipped by external force. In the elastic wave device, an external connection terminal, such as a bump or the like, is bonded for external connection. In a bonding process of the external connection terminal, stress is applied to a multilayer body including the piezoelectric thin film and the lamination layer film. This increases a risk that cracking, chipping, or the like of the piezoelectric thin film is generated.
In general, an elastic wave device is obtained by cutting a mother structure with a dicing machine. The force applied during the cutting with the dicing machine also raises a risk that cracking, chipping, or the like of the piezoelectric thin film is generated.
Further, there is a risk that interfacial peeling is generated in a multilayer body including the piezoelectric thin film at a time of connecting an external connection terminal, cutting with a dicing machine, or the like.
Furthermore, in the structure in which the piezoelectric thin film is provided on the lamination layer film, a wiring electrode needs to be provided so as to extend from an upper portion of the support substrate to an upper portion of the piezoelectric thin film. In this case, there is a problem in that breaking of the wiring electrode is likely to be generated.